This study takes advantage of electron beam CT measures of quantity of coronary artery calcification, measured CAD risk factors, and stored buffy coats on over 600 asymptomatic adults, and new data to be collected on 500 of their siblings. Understanding genetic susceptibility to asymptomatic atherosclerosis measured by quantity of CAC will increase our understanding of atherosclerosis and improve early identification of individuals who will benefit most from existing or new interventions.